1. Field of the Invention
Embodiments of the invention relate to an apparatus and method for driving a liquid crystal display device, which are capable of stabilizing a gate driving circuit through variation of levels of a gate driving voltage and a common voltage supplied to a liquid crystal panel in accordance with an ambient temperature, and preventing degradation of a picture quality through reduction of a level variation of an image display voltage depending on a kick-back voltage (ΔVp).
2. Discussion of the Related Art
Liquid crystal display (LCD) devices display an image using electrical and optical properties of liquid crystals. Liquid crystals exhibit different anisotropic properties in longer and shorter-axis directions of liquid crystal molecules in terms of a refractive index and a dielectric constant, and a molecular orientation and optical properties of liquid crystals may be easily controlled. Accordingly, LCD devices display an image by adjusting the orientation of liquid crystal molecules, thus controlling the light transmittance of the liquid crystals.
Such an LCD device includes a liquid crystal panel including a plurality of pixels arranged in the form of a matrix, a gate driver for driving gate lines of the liquid crystal panel, and a data driver for driving data lines of the liquid crystal panel.
Recently, a method of detecting a temperature of an LCD device or ambient temperature around the LCD device, and varying the level of a drive voltage in accordance with the detected temperature has been proposed. When the level of the drive voltage is linearly varied in accordance with the temperature of the LCD device or ambient temperature around the LCD device, it may be possible to stably drive the gate and data drive circuits of the LCD device, and to achieve an enhancement in the picture quality.
However, in a structure in which the gate drive circuit is formed at the liquid crystal panel, there is a difficulty in applying the method of varying the level of the drive voltage because thin film transistors (TFTs) of the gate drive circuit are made of amorphous silicon (a-Si). In other words, the liquid crystal panel which is of an active matrix type may have a difficulty in application thereof because the range of the voltage to operate liquid crystals is wide. Furthermore, TFTs have a large size to meet high-temperature operation characteristics thereof. For this reason, variation of current amount depending on temperature variation is increased. As a result, the gate drive circuit becomes unstable. In addition, when the level of a low drive voltage or a high drive voltage is varied, the variation width of an image display voltage depending on a kick-back voltage (ΔVp) may be increased. For this reason, degradation of picture quality caused by flicker or the like may occur.